struct ListNode* reverseList(struct ListNode* head)
{
	if(head==NULL)
	{
		return NULL;
	}
	struct ListNode* n1,*n2,*n3;
	n1=NULL;
	n2=head;
	n3=n2->next;
	while(n2)
	{
		n2->next=n1;
		n1=n2;
		n2=n3;
		if(n3)
		{
			n3=n3->next;
		}
	}
	return n1;
}
